Ligament tensioning device with cutting jig, and osteotomy method

ABSTRACT

A ligament-tensioning device for preparing for the implantation of a joint implant has a base body, having a first claw with a distal bearing surface which rests on a first bone, and a second claw which rests, with a proximal bearing surface, against a second bone. The second claw is displaceable parallel to the first claw. A cutting jig can be placed onto mounts of the base body of the ligament-tensioning device.

The invention relates to a ligament-tensioning device with a cutting jigfor joints of the human or animal body, and to a procedure for theosteotomy of these joints using the ligament-tensioning device withcutting jig according to the invention.

A ligament-tensioning device for non-spherical joints is known from WO00/78225 A1. The device described therein for tensioning ligaments innon-spherical joints in the human or animal body comprises a prismatic,cylindrical or plate-shaped base body with a right claw and a left claw,which have first bearing surfaces in one plane and can thus be broughtto bear in parallel on the joint-side surface of a first bone adjoininga non-spherical joint, and also a right handle and a left handle, aright tensioning lever and a left tensioning lever with two bearingsurfaces arranged parallel to the first bearing surfaces, it beingpossible to set a span Y between the respective bearing surfaces of theright tensioning lever and the right claw and the same or another span Xbetween the respective bearing surfaces of the left tensioning lever andthe left claw. The second bearing surfaces can be brought to bear on thejoint-side surface of a second bone adjoining the joint. Furthermore,the device comprises a right operating lever and a left operating lever,which, at the same time as the device is being held by one hand each onthe corresponding handle, can be actuated individually by the same handin each case, and a right parallel-displacement device and a leftparallel-displacement device, which can each be driven by thecorresponding operating lever and are connected to one tensioning levereach so that when the operating levers are moved the respective spans Xand Y can be set independently of one another. The parallel-displacementdevices are designed as four-bar-linkage lever mechanisms.

The disadvantage of the ligament-tensioning device known from WO00/78225 A1 is, in particular, that the provision of cut planes in adiseased joint for the purpose of introducing a prosthesis requiresfurther tools, which are attached to the joint independently of thetensioning device and as a result do not allow precise positioning andalignment, and reproducible, precise cutting.

Accordingly, the object on which the invention is based is to provide aligament-tensioning device and a procedure for tensioning with aparallel spreading movement the capsule-ligament structures of a jointto be provided with a prosthesis and at the same time enablingpresettable, adjustable and checkable cutting when preparing for andcarrying out the cuts required for providing a joint with a prosthesis.

The object is achieved with regard to the ligament-tensioning device bythe features of claim 1 and with regard to the procedure by the featuresof claim 20.

Further advantageous refinements of the invention are characterised inthe subclaims.

Advantageously, the cutting jig has projections with U-shaped slotswhich can be fitted into the mounts of the ligament-tensioning deviceand fixed in a catching manner by means of a locking element.

It is also advantageous that, by way of two corresponding scales whichdefine the particular position of the ligament-tensioning device, it ispossible to preset the width of the knee joint gap and the thickness ofthe implant to be introduced and check it at any time during theoperation.

The cutting jig advantageously has a saw guide which enables guidance ofthe bone saw with very few misalignments and a high degree of cuttingaccuracy. Furthermore, a cylindrical guide which enables furtheroperating instruments to be attached to the cutting jig is preferablyprovided.

In a further advantageous embodiment, the ligament-tensioning device canalso be designed as a bilateral ligament-tensioning device which enablessimultaneous provision for the medial and lateral joint part.

The invention is explained in more detail below with the aid of, inpart, schematic illustrations of the preparation for providing a humanknee joint with a prosthesis.

In the illustrations:

FIG. 1A shows a schematic, perspective view of a ligament-tensioningdevice with a cutting jig constructed in accordance with the invention,

FIG. 1B shows an enlarged illustration of the cutting jig illustrated inFIG. 1A,

FIGS. 2A-J show schematic, perspective illustrations of a distal femurosteotomy using the cutting jig according to the invention,

FIGS. 3A-F show schematic, perspective illustrations of a dorsal femurosteotomy using the cutting jig according to the invention, and

FIGS. 4A-J show schematic, perspective illustrations of femoral obliquecuts using the cutting jig according to the invention.

FIG. 1A shows, in a schematic, perspective general illustration, aligament-tensioning device 1, onto which a cutting jig 2 can be fitted.The cutting jig 2 can be fitted onto mounts 4 of the ligament-tensioningdevice 1 and locked to these mounts by means of a locking device 3.

The ligament-tensioning device 1 comprises a base body 5, which, forreliably transmitting the spreading force to the tibia, has a first claw6 with a bearing surface 7 which is distal in relation to the knee jointgap and rests on the femur in the case of a knee joint. Lying oppositethe first claw 6, a handle 8 is correspondingly attached to the basebody 5 and this handle permits one-handed holding and tensioning of theligament-tensioning device 1. Likewise corresponding to the arrangementof the first claw 6 and lying thereabove, the ligament-tensioning device1 comprises a tensioning lever 9 which is supported, by its proximalbearing surface 10 formed on a second claw 13, on the opposite portionof the joint to be treated, the tibia in the case of a knee joint. Thespreading action is produced by actuating the handle 8 together with anoperating lever 11 in each case either for a medial or lateral jointportion.

A parallel-displacement device 12 permits, with respect to the bearingsurfaces 7 and 10, a parallel displacement of the second claw 13 withthe bearing surface 10 relative to the first claw 6 with the bearingsurface 7. The second claw 13 is operatively connected to the tensioninglever 9 in this device. The parallel-displacement device 12 is designedas a four-bar linkage in the form of intersecting bars and comprisesfour levers 14, 15, 16, 17, a lever 14 on the tensioning lever and alever 17 on the base body being arranged in parallel, while the levers15 and 16 intersect. The four levers 14, 15, 16, 17 are connected to oneanother by means of five pivots 18, 19, 20, 21, 22. Two of the pivots18, 19 are displaceably mounted in the parallel levers 14, 17 inelongated holes 23, 24 running parallel to the bearing surfaces 7, 10.This construction of the parallel-displacement device 12 permits thelever 14 on the tensioning lever and the lever 17 on the base body to bemovable parallel to one another or apart from one another. The lengthsof the levers 14, 15, 16, 17 are chosen such that, for any span Xbetween the bearing surface 7 on the first claw 6 and the bearingsurface 10 on the second claw 13, which may be for example between 5 mmand 40 mm, there is a constant conversion ratio of 1:1 between thetensioning force applied manually to the handle 8 and to the operatinglever 11 and the distraction force exerted on the bones adjoining thejoint.

The size of the spreading force can be read off on a force indicator 25with a scale 26 and a movable indicating lever 27. The indicating lever27 is moved by the longitudinal bending of the operating lever part 28,which is bendable by a manually applied tensioning force, relative tothe other indicating lever 27, which is arranged in the manner of a forkand is not acted upon by this tensioning force. If the indicating lever27 and the operating lever part 28 are moved relative to one another bymeans of the tensioning force, the indicating lever 27 rotates about anaxis of rotation 29, whereby the manually applied tensioning force isindicated on the scale 26 by the indicating lever 27.

Furthermore, provision may be made between the handle 8 and theoperating lever 11 for a locking device, not illustrated specifically inFIG. 1A, which enables the ligament-tensioning device 1 to be locked ina particular position.

In the exemplary embodiment, the first claw 6 and the second claw 13 areformed as an outer claw 6 and an inner claw 13, which, in the relaxedstate of the ligament-tensioning device 1, lie in one plane and form acontinuous distal and proximal bearing surface. This facilitates theintroduction of the ligament-tensioning device 1 into the joint to betreated. On actuation of the ligament-tensioning device 1, the innerclaw 13 is parallel-displaced relative to the outer claw 6.

The base body 5 of the ligament-tensioning device 1 has a first scale34, which corresponds with a second scale 33 on a component 35connecting the lever 14 to the second claw 13. The scales 33 and 34serve for presetting and checking the width of the knee joint gap beforeand after the osteotomies preparing for the implantation. The precisefunction of the scales 33 and 34 is explained in more detail in FIG. 2Fand in the associated description.

The ligament-tensioning device 1 may also be designed as a bilateralligament-tensioning device 1 with two ligament-tensioning devices 1which act parallel to one another, can be connected to one another inany desired way, for example in the region of the base body 5, andenable simultaneous provision for the medial and the lateral jointportion. In this case, one or two cutting jigs 2 capable of being placedonto the ligament-tensioning device 1 are then to be provided as well.

FIG. 1B shows, in an enlarged view, the region of theligament-tensioning device 1 in which the cutting jig 2 is mounted. Thecutting jig 2 has two projections 30 of U-shaped design, forming slots31 which come into engagement with the mounts 4 on the base body 5 ofthe ligament-tensioning device 1 during the fitting of the cutting jig2. One of the mounts 4 is likewise of U-shaped design, the slot 31thereby formed having catches 32, which come into engagement with thelocking element 3 so that the cutting jig 2 is displaceably lockable onthe base body 5 of the ligament-tensioning device 1 in, for example,equidistant steps of, for example, 2 mm.

The cutting jig 2 furthermore has a cylindrical guide 36, into whichfurther instruments for carrying out or positioning the osteotomies canbe introduced. This may, for example, as can be seen in FIGS. 3A to 3E,be an aligning jig 48, which enables fixed positioning of the cuttingjig 2 at a specified angle.

For guidance of a feeler gauge or the bone saw to be used for theosteotomies, provision is made for a saw guide 37 which is preferablyformed at right angles in the cutting jig 2. The saw guide 37 ensuresguidance of the saw in a manner free from deviation, whereby a highdegree of accuracy with few misalignments is achieved during theresection of the bone parts concerned.

The following FIGS. 2A to 2J to 4A to 4J show the working steps requiredto prepare the femur 38 in the region of the knee joint for theimplantation of an implant which replaces a femur condyle 39 destroyed,for example, by arthrosis. The preparatory measures on the tibia 40 canbe carried out by means of resection methods which are already known.

FIGS. 2A to 2J show the preparatory work for the distal femur osteotomy.For this purpose, firstly, as not explained in any more detail, thetibia 40 is appropriately prepared, as can already be seen in FIG. 2A.It can also be seen from FIG. 2A how the size of the femur 39 to beresected is determined by means of a femur size gauge 41. Several sizes,e.g. five, for correctly determining the size of the femur 38 areavailable to the surgeon for this. Of interest for the distal femurosteotomy is firstly the mark, indicated by 42 in FIG. 2A, which is madeon the femur 38. For this, the leg is firstly put into a 90° positionand, after positioning the femur size gauge 41 on the ventral end, amark 42 is made on the femur 38 with the aid of a cautery knife. Theposition of this mark is roughly the boundary between the femorotibialand the femoropatellar part of the femur 38. After removing the femursize gauge 41, the mark 42 made is visible on the femur 38, as can beseen in FIG. 2B.

In the next step, as illustrated in FIG. 2C, the cutting jig 2 ispremounted on the ligament-tensioning device 1, the cutting jig 2 beingfitted onto the ligament-tensioning device 1, as described in FIGS. 1Aand 1B. With the aid of the locking element 3, the thickness of theinlay implant to be inserted later can be set at between 5 and 11 mm in2 mm steps, as already mentioned above.

After that, with the leg extended, the ligament-tensioning device 1 withthe cutting jig 2 mounted is introduced into the joint gap 43. In sodoing, the distal bearing surface 7 of the first claw 6 of theligament-tensioning device 1 rests on the cut tibia surface 44 which hasalready been prepared.

Now, the ligament-tensioning device 1 is spread with the desired force.A feeler gauge 45 is passed through the saw guide 37 of the cutting jig2 until the feeler gauge 45 rests against the femur 38. Now, it ischecked whether the mark 42 on the femur 38 is in line with the feelergauge 45. This can be seen from FIGS. 2D and 2E. The arrow 61 in FIG. 2Eshows clearly that the feeler gauge 45 is now resting in the desiredposition against the mark 42 and that the cutting path for the distalfemur osteotomy is correctly set. This can be optimally set by aspecific movement of the lower leg.

After the spreading of the ligament-tensioning device 1, the thicknessof the distal femur condyle 39 to be resected can be read off using thegradation on the scale 34 of the ligament-tensioning device 1 before theactual resection. The distance is determined from the difference betweenthe zero line 46 and the chosen thickness of the implant to be insertedlater. In FIG. 2F, the condyle thickness to be resected is 7 mm if a 5mm inlay implant is selected. If the measured value is less than 5 mm,the cutting jig 2 has to be set accordingly for a greater implantthickness, e.g. for 7 or 9 mm. If the measured difference is greaterthan 8 mm, e.g. for a set condyle height of 5 mm, a further resection ofthe tibia 40 must be performed.

After the preparatory work, the distal femur osteotomy is carried out bymeans of a saw 47 passed through the saw guide 37 of the cutting jig 2.This is illustrated in FIG. 2G.

After carrying out the distal femur osteotomy, the ligament-tensioningdevice 1 is relaxed and removed from the knee joint gap 43. The cuttingjig 2 is demounted from the ligament-tensioning device 1. After that,the ligament-tensioning device 1 is again introduced into the joint gap43. Now, the width of the joint gap 43 is checked by spreading theligament-tensioning device 1. The zero line 46 must correspond to thechosen implant thickness, as illustrated in FIG. 2H and FIG. 2J.

In the example, the correspondence with the preselected implantthickness of 5 mm can be seen, since the zero line 46 of the scale 33now coincides with the 5 mm line of the scale 34, as illustrated in FIG.2J. In the event of deviations of more than one millimetre, a correctionmust be made by further resection of the tibia 40 or of the distal femurcondyle.

FIGS. 3A to 3F show the step of the dorsal femur osteotomy which nowfollows. For this purpose, the leg is firstly put into a 90° flexedposition again.

The cutting jig 2 is again premounted on the ligament-tensioning device1. In so doing, the cutting jig 2 is set to the same inlay implantthickness as in the preceding distal femur osteotomy. The premountedligament-tensioning device 1 is now introduced into the joint gap 43.After that, the ligament-tensioning device 1 is spread with the desiredforce.

Now, as illustrated in FIG. 3A, an aligning jig 48 for the dorsal femurcut is pushed into a cylindrical guide 49 of the cutting jig 2. Thealigning jig 48 is now displaced until it is in contact with the distalfemur surface 50, as illustrated in FIG. 3B. Now, as shown in FIG. 3C,by moving the lower leg, the position of the aligning jig 48 has to beset so that the latter rests evenly against the distal femur surface 50.

After checking the spreading force, the aligning gauge 48 can be fixedto the distal femur surface 50 using a bone nail 51, as illustrated inFIG. 3D. The system is thereby stabilised. It must be ensured here thatthe aligning jig 48 is still resting evenly against the distal femursurface 50.

After that, the saw 47 is introduced through the saw guide 37 of thecutting jig 2 as in the distal femur osteotomy, and the dorsal femurosteotomy is carried out. Care must be taken here to protect theligamentary structures.

After carrying out the dorsal femur osteotomy, the bone nail 51 and theligament-tensioning device 1 are removed. After that, the cutting jig 2is removed from the ligament-tensioning device 1. Where necessary,dorsal osteophytes are removed by subsequent treatment.

After that, as illustrated in FIG. 3F, the ligament-tensioning device 1is once again introduced into the joint gap 43. The flexion gap ischecked using the marks on the scale, as already described in FIGS. 2Ato 2J. If the desired flexion gap does not correspond to the measuredgap, it is necessary to carry out further resection of the dorsal femursurface 52 (repetition of the steps illustrated in FIGS. 3A to 3F).

FIGS. 4A to 4J illustrate the working steps for the concluding femoraloblique cuts. In this case, firstly, as can be seen from FIG. 4A, adrilling jig 53, required to drill holes for the attachment of anoblique-cutting block, is mounted on the ligament-tensioning device 1.The drilling jig 53 is pushed into the mounts 4, which are also used forthe cutting jig 2. The drilling jig 53 must be mounted as far as it willgo on the ligament-tensioning device 1, as can be seen from FIG. 4B.

After that, the ligament-tensioning device 1 is introduced into the kneejoint gap 43 as in the previous steps, as can be seen from FIG. 4C.After that, two drilling sleeves 54 are pushed in through thedrilling-jig 53 until they butt against the distal femur surface 52.This is illustrated in FIG. 4D. Furthermore, as can be seen from FIG.4E, the ligament-tensioning device 1 is spread with the desired force.It is again checked whether the drilling jig 53 is resting flat on theligament-tensioning device 1. Now, the aligning jig 48, which hasalready been used in the dorsal femur osteotomy, is pushed into thecylindrical guide 55, as illustrated in FIG. 4E, and the position of thealigning jig 48 is again set so that the aligning jig 48 rests evenlyagainst the distal femur surface 50. When the tensioner is setprecisely, the zero mark 46 should correspond to the desired inlaythickness 34.

After a further check of the optimal tension of the ligament-tensioningdevice 1, two holes 56 with a drilling depth of about 35 mm and adiameter of about 3.2 mm are drilled into the distal femur surface 50,according to FIG. 4F. After that, the ligament-tensioning device 1 isloosened and removed from the knee joint gap 43.

FIG. 4G shows the oblique-cutting jig 57, suitably selected in eachcase, being pushed into the two holes 56 by way of two correspondingpins 58. The oblique-cutting jig 57 can be pushed in, or else driven inwith guidance by means of holding pincers. The oblique-cutting jig 57 isdesigned so that it rests straight against the distal femur surface 50and the dorsal femur surface 52.

The oblique-cutting jig 57 has a bearing surface 59 for making thefirst, ventral oblique cut and a saw guide 60 for the second, dorsaloblique cut.

FIG. 4H shows the ventral oblique cut, which is made up to the ventralmark 42, which has been made on the femur 38 at the start of theoperation using a cautery knife.

FIG. 4J shows the concluding dorsal oblique cut, the saw 47 being passedthrough the saw guide 60.

After removal of the oblique-cutting jig 57, finishing work is carriedout on the tibia 40 and the femur 38, and finally the femoral and tibialimplants are implanted.

The invention is not restricted to the exemplary embodiment illustratedand—as already mentioned—can also be employed for bilateral implants inthe knee joint. The basic principle of providing mounts for a cuttingjig on a suitably adapted ligament-tensioning device can also be appliedto other joints.

1. Ligament-tensioning device for preparing for the implantation of ajoint implant, with a base body, having a first claw with a distalbearing surface which rests on a first bone, and a second claw whichrests, with a proximal bearing surface, against a second bone, thesecond claw being displaceable parallel to the first claw, characterisedin that wherein a cutting jig can be placed onto mounts of the base bodyof the ligament-tensioning device.
 2. Ligament-tensioning deviceaccording to claim 1, wherein the cutting jig has U-shaped projectionswith slots.
 3. Ligament-tensioning device according to claim 2, whereinthe projections of the cutting jig can be brought into engagement withthe mounts.
 4. Ligament-tensioning device according to claim 1, whereinthe cutting jig can be is fixed to the mounts by means of a lockingelement.
 5. Ligament-tensioning device according to claim 1, wherein themounts comprise catches.
 6. Ligament-tensioning device according toclaim 5, wherein the catches are equidistant.
 7. Ligament-tensioningdevice according to claim 5 wherein the cutting jig is displaceable onthe mounts in a catching manner.
 8. Ligament-tensioning device accordingto claim 1, wherein the first claw and the second claw are displaceableparallel to one another by means of a parallel-displacement device. 9.Ligament-tensioning device according to claim 8, wherein a first scaleis provided on a component connecting the second claw to theparallel-displacement device.
 10. Ligament-tensioning device accordingto claim 8, wherein a second scale is provided on the base body. 11.Ligament-tensioning device according to claim 10, wherein the first andsecond scales can be brought into coincidence so that the height of animplant to be inserted into the joint to be treated can be preset. 12.Ligament-tensioning device according to claim 1, wherein the cutting jighas a cylindrical guide.
 13. Ligament-tensioning device according toclaim 12, wherein an aligning jig can be introduced into the cylindricalguide.
 14. Ligament-tensioning device according to claim 13, wherein thealigning jig can be fixed to the second bone by means of a bone nail.15. Ligament-tensioning device according to claim 1, wherein the cuttingjig has a saw guide.
 16. Ligament-tensioning device according to claim1, wherein a drilling jig can be fitted onto the ligament-tensioningdevice.
 17. Ligament-tensioning device according to claim 16, whereinthe drilling jig can be placed onto the mounts of the base body. 18.Ligament-tensioning device according to claim 1, wherein theligament-tensioning device is a bilateral ligament-tensioning device.19. Ligament-tensioning device according to claim 18, wherein theligament-tensioning device has a force indicator.
 20. Procedure forpreparing a joint for the implantation of a joint implant by means of aligament-tensioning device with cutting jig, the ligament-tensioningdevice comprising a base body, having a first claw with a distal bearingsurface which rests on a first bone, and a second claw which rests, witha proximal bearing surface, against a second bone, the second claw beingdisplaceable parallel to the first claw, and the cutting jig being ableto be placed onto mounts of the base body of the ligament-tensioningdevice, the procedure comprising the steps of: carrying out a distalfemur osteotomy while simultaneously tensioning the ligaments by meansof the ligament-tensioning device, carrying out a dorsal femur osteotomywhile simultaneously tensioning the ligaments by means of theligament-tensioning device, and carrying out femoral oblique cuts whilesimultaneously tensioning the ligaments by means of theligament-tensioning device.
 21. Procedure according to claim 20, whereinthe joint implant is a knee joint implant which is implanted into thetibia and the femur.
 22. Procedure according to claim 20, wherein thefirst procedure step comprises the substeps of: premounting the cuttingjig on the ligament-tensioning device, setting the desired thickness ofthe implant, introducing the ligament-tensioning device into the kneejoint gap, spreading the ligament-tensioning device with a predeterminedforce, introducing a feeler gauge into a saw guide of the cutting jig,checking the distal femur cutting path, carrying out the distal femurosteotomy by means of a saw passed through the saw guide of the cuttingjig, removing the ligament-tensioning device from the knee joint gap,demounting the cutting jig, reintroducing the ligament-tensioning deviceinto the knee joint gap, and checking the width of the knee joint gap bymeans of scales s present on the ligament-tensioning device. 23.Procedure according to claim 20, wherein the second procedure stepcomprises the substeps of: flexing the leg, premounting the cutting jigon the ligament-tensioning device, introducing the ligament-tensioningdevice into the knee joint gap, spreading the ligament tensioning devicewith a predetermined force, pushing the aligning jig for the dorsalfemur cut into a cylindrical guide of the cutting jig, displacing thealigning jig up against the distal femur surface, adjusting the lowerleg until the aligning jig rests evenly against the distal femursurface, fixing the aligning jig to the distal femur surface by means ofa bone nail, dorsal femur osteotomy, removing the bone nail, removingthe ligament-tensioning device from the knee joint gap, demounting thecutting jig, removing the dorsal osteophytes, reintroducing theligament-tensioning device into the knee joint gap, and checking thewidth of the knee joint gap by means of scales present on theligament-tensioning device.
 24. Procedure according to claim 20, whereinthe third procedure step comprises the following substeps of: mounting adrilling jig for an oblique-cutting jig as far as it will go on theligament-tensioning device, introducing the ligament-tensioning deviceinto the knee joint gap, pushing two drilling sleeves through thedrilling jig up to the distal femur surface, spreading theligament-tensioning device with a predetermined force, pushing thealigning jig for the dorsal femur cut into a cylindrical guide of thedrilling jig, displacing the aligning jig up against the distal femursurface, adjusting the lower leg until the aligning jig rests evenlyagainst the distal femur surface, drilling two holes in the distal femursurface, removing the ligament-tensioning device from the knee jointgap, pushing the chosen oblique-cutting jig into the two holes,resecting the ventral oblique cut up to the mark, and resecting thedorsal oblique cut.